Chemical threats for the sentinel Pygoscelis adeliae from the Ross Sea (Antarctica): Occurrence and levels of persistent organic pollutants (POPs), perfluoroalkyl substances (PFAS) and mercury within the largest marine protected area worldwide

: The Ross Sea Marine Protected Area (RS-MPA) hosts endemic species that have to cope with multiple threats, including chemical contamination. Adèlie penguin is considered a good sentinel species for monitoring pollutants. Here, 23 unhatched eggs, collected from three colonies along the Ross Sea coasts, were analysed to provide updated results on legacy pollutants and establish a baseline for newer ones. Average sum of polychlorinated biphenyls (∑PCBs) at the three colonies ranged 20.9-24.3 ng/g lipid weight (lw) and included PCBs IUPAC nos. 28, 118, 153, 138, 180. PCBs were dominated by hexachlorinated congeners as previously reported. Hexachlorobenzene (HCB) and p,p'-dichlorodiphenyldichloroethylene (p,p'-DDE) ranged between 134 and 166 and 181-228 ng/g lw, respectively. Overall, ∑PCBs was exceeded by pesticides, contrary to previous studies from the Ross Sea. Sum of polybrominated diphenyl ethers (∑PBDEs) ranged between 0.90 and 1.18 ng/g lw and consisted of BDE-47 (that prevailed as expected, representing 60-80 % of the ∑PBDEs) and BDE-85. Sum of perfluoroalkyl substances (∑PFAS) ranged from 1.04 to 1.53 ng/g wet weight and comprised five long-chain perfluorinated carboxylic acids (PFCAs), perfluorooctane sulfonate (PFOS), perfluorohexane sulfonate (PFHxS) and perfluorooctanoic acid (PFOA); perfluorooctane sulfonamide (PFOSA) was also detected. The PFAS profile was dominated by PFCAs as already observed in Arctic seabirds. Mercury ranged from 0.07 to 0.15 mg/kg dry weight similarly to previous studies. Legacy pollutants confirmed their ongoing presence in Antarctic biota and their levels seemed mostly in line with the past, but with minor variations in some cases, likely due to continued input or release from past reservoirs. PFAS were reported for the first time in penguins from the Ross Sea, highlighting their ubiquity. Although further studies would be useful to increase the sample size and accordingly improve our knowledge on spatial and temporal trends, this study provides interesting data for future monitoring programs within the RS-MPA that will be crucial to test its effectiveness against human impacts.